UV light absorbers and hindered amine light stabilizers, abbreviated herein as “HALS” are known to be effective stabilizers for polyolefins. In addition to polyolefins, HALS have been used to improve the weatherability of polyesters that contain aromatic repeating units such as, for example, linear polyalkylene terephthalates, copolyester elastomers, polycarbonates and mixtures of these polymers. Weatherable, aliphatic copolyesterether compositions comprising a combination of HALS, UV absorbers, phosphites, and hindered phenol antioxidants also are known.
Certain UV absorbers, when used alone and in combination with HALS, often do not effectively control and can cause an increase in the haze, color, and brittleness of aliphatic polyesters under weathering conditions. In addition, certain combinations of HALS and UV absorbers often are not compatible with aliphatic polyesters and can cause haze and color to appear in the polyester before the polymer is exposed to weathering conditions. Phosphites are sometimes added to control color, but the combination of certain HALS and phosphites also can produce haze. Thus, there is a need within the art for a stabilized polyester composition that will withstand the effects of weathering. There is a also need for a stabilized aliphatic polyester composition having a combination of UV absorbers and HALS that will not show a high level of color or haze before exposure to weathering conditions. Such stabilized aliphatic polyester compositions would have commercial applications in areas where aliphatic polyesters are exposed to sunlight and to the outside environment such as, for example, in signage, packaging, computer touchpads, and metal laminates.